Salinities as low as 14.0 p.p.t. were observed 

 along the Louisiana coast. These low- salinity 

 waters apparently flowed westward and ex- 

 tended over the Continental Shelf along the 

 Texas coast where salinities were as low as 

 32.0 p.p.t. 60 miles offshore (fig. 2). This 

 freshening of coastal waters, coupled with an 

 extensive shoreward intrusion of high- salinity 

 waters, resulted in a steep salinity gradient 

 along the Louisiana coast. 



The distribution of salinities in July and 

 August suggested an apparent shift in surface 

 currents. The intrusion of high- salinity waters 

 observed earlier along the Louisiana coast 

 had shifted and was now evident along the 

 central Texas coast. 



The effects of decreased river discharge 

 became apparent in the salinity distribution 

 from September to December. Conditions simi- 

 lar to those from January to March prevailed 

 generally throughout the study area. Isohalines 

 paralleled the coast and ranged from 30.0 

 p.p.t. inshore to 36.5 p.p.t. offshore. The only 

 offshore extension of moderately low- salinity 

 water (34.0 p.p.t.) was in September, south of 

 Morgan City, La., and extended offshore beyond 

 the limit of the study area. 



Surface Temperatures 



Seasonal warming and cooling of surface 

 waters in 1964 were closely related to seasonal 

 changes in prevailing air temperatures . Yearly 

 temperature ranges, however, decreased with 

 increase in distance from the coast. Shore- 

 ward of the 7^-fath. contour, surface water 

 temperatures varied over a range of 21.0 °C. 

 (37.80F.), but they varied only 14.0°C. 

 (25.3 °F.) over the 60 fath. contour. Lowest 

 temperatures (10.0°C. or 50.0°F. inshore 

 and 19.0 OC. or 66.2 ° F. offshore) occurred 

 in January off the Louisiana coast; highest 

 temperatures (31.0°C. or 87.80F.), also 

 along the Louisiana coast, were recorded in 

 August. 



Bottom Temperatures 



Warming and cooling at the bottom are 

 not the steady progressions seen at the sur- 

 face. Bottom values reach their maximum 

 at the time of fall turnover- -during late sum- 

 mer in the shallower waters and gradually 

 later offshore where conditions are unifornn 

 in December or January. Bottom tempera- 

 tures shoreward of the Tj-fath. stations fluctu- 

 ated over a range of 21.0OC. (37.8 o F.), but 

 varied only 3.0 OC. (5.4 ^F.) at the outermost 

 station (60 fath.). The highest bottom values 

 (30.0 °C. or 86.0 OF.) were inshore in August 

 and offshore (19.0OC, or 66.2 °F.) between 

 October and January. During September and 

 December, when offshore bottom temperatures 

 were still increasing, coastal waters were 



cooling; consequently, cooler temperatures 

 prevailed inside and outside a zone of warmer 

 waters located between the 15- and 25-fath. 

 contours. 



Studies of Currents 



Plans for a more intensive study of water 

 currents and their role in larval shrimp trans- 

 port from offshore spawning grounds to estua- 

 rine systems have been outlined and prelimi- 

 nary phases completed. In May 1965, a 24-hr. 

 anchor station was maintained through use of 

 a transistorized savonius-type current meter 

 and several Carruthers gelatin bottles to 

 measure currents. The aims of this work 

 were: (1) to develop a system and technique 

 for making gelatin-bottle casts, (2) to compare 

 the results from each type of instrument, and 

 (3) to measure existing water currents on 

 spawning grounds of white shrimp. 



A position off the Louisiana coast in the 

 center of fairly extensive white shrimp fishing 

 was selected for current studies. Hourly ob- 

 servations, with both instruments, were made 

 at depths of 10 and 23 ft. Additional observa- 

 tions were made 1 ft. above bottom with the 

 gelatin bottle and 10 ft. above the bottom with 

 the Savonius current meter. An efficient system 

 was developed for making gelatin-bottle casts, 

 and results showed similar readings from the 

 different instrunnents (fig. 3). At depths of 10 

 and 23 ft., the difference between instruments 

 in resultant current directions did not exceed 

 7 , and resultant velocities varied no more 



Figures. — Hourly current measurements obtained simul- 

 taneously with the galatin bottle and the savonius current 

 meter. May 24, 1965. 



